For attaching hardware to 3/4 plywood, it is recommended to use 8 or 10 screws.
The recommended screw size for attaching hardware to 3/4 plywood is typically 8 or 10 screws.
The recommended screw length for attaching hardware to 1/2 inch plywood is typically 1 inch.
The recommended screw length for attaching hardware to 3/4 inch plywood is 1-1/4 inches.
For 1/2 inch plywood, a 6 or 8 screw size is typically recommended.
For 3/4 inch plywood, a 1-1/4 inch pocket hole screw is typically recommended.
For 1/2 inch plywood, a 1-1/4 inch pocket hole screw is typically recommended.
The recommended screw size for attaching the bracket to the wall is typically a 8 or 10 screw.
The recommended pocket screw size for 3/4 inch plywood is 1-1/4 inch.
The standard m5 screw size for attaching components in electronic devices is 5 millimeters in diameter.
The recommended pocket hole screw size for 3/4 inch plywood is 1 1/4 inch.
Attaching the sides of the bookcase to the shelves will secure it however you will have to figure out a method. Drilling small pilot holes and running some screws through the sides into the shelves should work well, however, only if the material is solid wood and may work with plywood. If the material is plywood or particle board you will need to consider using gussets, either made from wood or, better, pre-formed steel brackets available at any hardware store. You would then screw the "L" shaped metal brackets to the underside of the shelves and then screw them to the bookcase sides. You may also consider lightening the load, such as finding another place to store your lead crystal collection.
An easier solution is to take the screw to a hardware store and compare the screw to the screw size they have available. As long as it's not too long, it should work just fine.